5. THE OSIRIS INSTRUMENT ON THE ODIN SATELLITE
To the athors knowledge, the OSIRIS instrument onboard the Odin satellite was the only spaceborne instrument that where able to detect any signals from the 6'th December 2002 event. The OSIRIS instrument measure limb radiance height profiles from 280 nm to 800 nm.
During the orbit #9726 the Odin spacecraft scanned in altitude from 5 to 70 km. Enhanced red spectra were observed from 12:47:09 to 12:47:43 UT. The spectra originated from an area that spanned from (72.67°N, 53.47°E) to (74.43°N,49.94°E), which is approximately South East of Longyearbyen. The table below show the spectra obtained of the event from OSIRIS.
The spectra show O2 A-band absorption at 762 nm. The water vapour absorption feature is evident at ~730 nm and the O2 B-band at ~690 nm is also evident. Note that the A-band absorption is unreliable as the background signal that is subtracted (mostly dark current) does have significant A-band emissions.
The spatial resolution of OSIRIS is about 1 km in altitude by 30 km parallel to the Earth's surface. The estimated height profile at 800 nm is given in Table 5.2.
|Altitude [km]||Intensity (800nm) [R/Å]|
Note that the above profile is a height profile of the OSIRIS line of sight integrated signal. Figure 5.1 shows the result.
Figure. 5.1 Line of sight integrated height profile at 800 nm from OSIRIS Odin orbit #9726, 06.12.2002.
It is clear from the above data that the Odin/OSIRIS recorded the red-sky event observed at Longyearbyen. The height profile resembels a scattering layer with an upper altitude around 20 - 25 km. The brightness seen by OSIRIS are of the same order of magnitude (a couple of hundred R/Å) as seen by the instrumentation at the Auroral station in Adventdalen.